When creating a new item, if a user accidentally add preprocessing, but don't add parameters, then error message when trying to save an item is:

Incorrect value for field "params": first parameter is expected.

Page is automatically reloaded to the Item configuration tab, nor the preprocessing tab which may cause some frustration to identify where exactly is missing parameter.

Should be something like:

Incorrect value for field "params": first parameter is expected in Regular expression preprocessing.